At a certain proficiency level you know the difference (and can apply that to action) at all times.
At all times? That might end up in the category of famous last words.
...I think plenty of shooters can proficiently carry different pistols effectively.
Most of us can
carry anything "effectively". The important question is one of how we will react at that instant that counts, and how quickly we will draw, present, and fire.
I'm not saying you should do something you aren't comfortable with.
The question is whether that "comfort" can be tested.
I was
quite comfortable carrying a striker fired pistol with a manual safety that was similar in
operation to a 1911, but somewhat different in
location. I practiced extensively, and I convinced myself that I knew what I was doing.
I took a course under a well-known trainer who
strongly advised against carrying a gun that required a separate operation to disengage a safety--the exception being the 1911, for obvious reasons.
And guess what--the first time I failed to disengage that safety happened to occur in a class when he was watching--not a high stress situation, but perhaps with some performance anxiety. I don't care whether it was the result of a "physical handicap" or a "mental handicap". It happened, and under different circumstances, it could well have led to disaster.
That was also the last time. He told me to keep the safety disengaged for the rest of the two day class. And then I replaced the gun with one with a grip safety only.
That trainer now carries the same gun.
I just think it's pretentious for a body to impose their skill-set on others which is how I see the original post and a number of responses.
Not at all.
It is simply the considered advice of experienced trainers. Some of them see a dozen or more students training in long two day sessions more than once a week. And they share their observations with others.
They see more different techniques, different holsters, different carry positions, and different firearms used under high-performance training conditions than I have, or than most of us do.
I choose to follow their advice.